rft_genericrft_genericRftGenericRftGeneric (Operator)


rft_genericrft_genericRftGenericRftGeneric — Compute the real-valued fast Fourier transform of an image.


rft_generic(Image : ImageFFT : Direction, Norm, ResultType, Width : )

Herror rft_generic(const Hobject Image, Hobject* ImageFFT, const char* Direction, const char* Norm, const char* ResultType, const Hlong Width)

Herror T_rft_generic(const Hobject Image, Hobject* ImageFFT, const Htuple Direction, const Htuple Norm, const Htuple ResultType, const Htuple Width)

void RftGeneric(const HObject& Image, HObject* ImageFFT, const HTuple& Direction, const HTuple& Norm, const HTuple& ResultType, const HTuple& Width)

HImage HImage::RftGeneric(const HString& Direction, const HString& Norm, const HString& ResultType, Hlong Width) const

HImage HImage::RftGeneric(const char* Direction, const char* Norm, const char* ResultType, Hlong Width) const

HImage HImage::RftGeneric(const wchar_t* Direction, const wchar_t* Norm, const wchar_t* ResultType, Hlong Width) const   (Windows only)

static void HOperatorSet.RftGeneric(HObject image, out HObject imageFFT, HTuple direction, HTuple norm, HTuple resultType, HTuple width)

HImage HImage.RftGeneric(string direction, string norm, string resultType, int width)


rft_genericrft_genericRftGenericRftGenericRftGeneric computes the fast Fourier transform of the input image ImageImageImageImageimage. In contrast to fft_genericfft_genericFftGenericFftGenericFftGeneric, fft_imagefft_imageFftImageFftImageFftImage, and fft_image_invfft_image_invFftImageInvFftImageInvFftImageInv, the fact that the input image in the forward transform is a real-valued image (i.e., not a complex image) is used. In this case, the complex output image has a redundancy. The values in the right half of the image are the complex conjugates of the corresponding values in the left half of the image. Consequently, runtime and memory can be saved by only computing and storing the left half of the complex image.

The parameter ResultTypeResultTypeResultTypeResultTyperesultType can be used to specify the result image type of the reverse transform (DirectionDirectionDirectionDirectiondirection = 'from_freq'"from_freq""from_freq""from_freq""from_freq"). In the forward transform (DirectionDirectionDirectionDirectiondirection = 'to_freq'"to_freq""to_freq""to_freq""to_freq"), ResultTypeResultTypeResultTypeResultTyperesultType must be set to 'complex'"complex""complex""complex""complex".

The parameter direction determines whether the transform should be performed to the frequency domain or back into the spatial domain. For DirectionDirectionDirectionDirectiondirection = 'to_freq'"to_freq""to_freq""to_freq""to_freq" the input image must have a real-valued type, i.e., a complex image may not be used as input. All image types that can be converted into an image of type real are supported. In this case, the output is a complex image of dimension (w/2+1)*h, where w and h are the width and height of the input image. In this mode, the exponent -1 is used in the transform (see fft_genericfft_genericFftGenericFftGenericFftGeneric). For DirectionDirectionDirectionDirectiondirection = 'from_freq'"from_freq""from_freq""from_freq""from_freq", the input image must be complex. In this case, the size of the input image is insufficient to determine the size of the output image. This must be done by setting WidthWidthWidthWidthwidth to a valid value, i.e., to 2*w-2 or 2*w-1, where w is the width of the complex image. In this mode, the exponent 1 is used in the transform.

The normalizing factor can be set with NormNormNormNormnorm, and can take on the values 'none'"none""none""none""none", 'sqrt'"sqrt""sqrt""sqrt""sqrt" and 'n'"n""n""n""n". The user must ensure the consistent use of the parameters. This means that the normalizing factors used for the forward and backward transform must yield w*h when multiplied.


The transformation is always performed for the entire image, i.e., the domain of the image is ignored.

Execution Information


ImageImageImageImageimage (input_object)  (multichannel-)image(-array) objectHImageHImageHobject (byte / direction / cyclic / int1 / int2 / uint2 / int4 / real / complex)

Input image.

ImageFFTImageFFTImageFFTImageFFTimageFFT (output_object)  image(-array) objectHImageHImageHobject * (byte / direction / cyclic / int1 / int2 / uint2 / int4 / real / complex)

Fourier-transformed image.

DirectionDirectionDirectionDirectiondirection (input_control)  string HTupleHTupleHtuple (string) (string) (HString) (char*)

Calculate forward or reverse transform.

Default value: 'to_freq' "to_freq" "to_freq" "to_freq" "to_freq"

List of values: 'from_freq'"from_freq""from_freq""from_freq""from_freq", 'to_freq'"to_freq""to_freq""to_freq""to_freq"

NormNormNormNormnorm (input_control)  string HTupleHTupleHtuple (string) (string) (HString) (char*)

Normalizing factor of the transform.

Default value: 'sqrt' "sqrt" "sqrt" "sqrt" "sqrt"

List of values: 'n'"n""n""n""n", 'none'"none""none""none""none", 'sqrt'"sqrt""sqrt""sqrt""sqrt"

ResultTypeResultTypeResultTypeResultTyperesultType (input_control)  string HTupleHTupleHtuple (string) (string) (HString) (char*)

Image type of the output image.

Default value: 'complex' "complex" "complex" "complex" "complex"

List of values: 'byte'"byte""byte""byte""byte", 'complex'"complex""complex""complex""complex", 'cyclic'"cyclic""cyclic""cyclic""cyclic", 'direction'"direction""direction""direction""direction", 'int1'"int1""int1""int1""int1", 'int2'"int2""int2""int2""int2", 'int4'"int4""int4""int4""int4", 'real'"real""real""real""real", 'uint2'"uint2""uint2""uint2""uint2"

WidthWidthWidthWidthwidth (input_control)  integer HTupleHTupleHtuple (integer) (int / long) (Hlong) (Hlong)

Width of the image for which the runtime should be optimized.

Default value: 512

Suggested values: 128, 160, 192, 256, 320, 384, 512, 640, 768, 1024, 2048


rft_genericrft_genericRftGenericRftGenericRftGeneric returns 2 (H_MSG_TRUE) if all parameters are correct. If the input is empty the behavior can be set via set_system(::'no_object_result',<Result>:)set_system("no_object_result",<Result>)SetSystem("no_object_result",<Result>)SetSystem("no_object_result",<Result>)SetSystem("no_object_result",<Result>). If necessary, an exception is raised.

Possible Predecessors

optimize_rft_speedoptimize_rft_speedOptimizeRftSpeedOptimizeRftSpeedOptimizeRftSpeed, read_fft_optimization_dataread_fft_optimization_dataReadFftOptimizationDataReadFftOptimizationDataReadFftOptimizationData

Possible Successors

convol_fftconvol_fftConvolFftConvolFftConvolFft, correlation_fftcorrelation_fftCorrelationFftCorrelationFftCorrelationFft, phase_correlation_fftphase_correlation_fftPhaseCorrelationFftPhaseCorrelationFftPhaseCorrelationFft, convert_image_typeconvert_image_typeConvertImageTypeConvertImageTypeConvertImageType, power_bytepower_bytePowerBytePowerBytePowerByte, power_realpower_realPowerRealPowerRealPowerReal, power_lnpower_lnPowerLnPowerLnPowerLn, phase_degphase_degPhaseDegPhaseDegPhaseDeg, phase_radphase_radPhaseRadPhaseRadPhaseRad


fft_genericfft_genericFftGenericFftGenericFftGeneric, fft_imagefft_imageFftImageFftImageFftImage, fft_image_invfft_image_invFftImageInvFftImageInvFftImageInv